Viscose spinning process



United States Patent D VISCOSE SPINNING PROCESS Joseph W. Schappel, Morton,

Viscose Corporation, of Delaware Pa., assignor to American Philadelphia, Pa., a corporation 7 Claims. (Cl. 18-54) This invention relates to fibers, yarns, fabrics and other articles comprising regenerated cellulose and a heat-hardened reaction product or condensation product of a linear polymer of a monoamide and formaldehyde, which articles are characterized by markedly decreased water-sensitivity as compared to conventional regenerated cellulose articles.

An important advantage of regenerated cellulose yarns is that, after initial drying thereof in the course of their production, those yarns can regain from about 7 to 11% of moisture from the atmosphere, under normal temperature and humidity conditions. Thi ability to regain moisture from the atmosphere is a distinct asset of the regenerated cellulose yarns and is responsible for the desirably soft hand or feel of regenerated cellulose fabrics. On the other hand, regenerated cellulose yarns are very water-sensitive and normally pick up and retain an excessive amount of water when they are exposed to water or aqueous media, the amount of water normally picked up and retained being considerably higher than 50% and up to 100% or more by Weight. This is undesirable because it results in excessive swelling of the yarns with danger of distortion, the tendency of fabrics comprising the yarns to shrink progressively on repeated laundering, and protracted drying times. Also, the absorption and retention of large amounts of water by crimped regenerated cellulose fibers or yarns, as such or as they occur in fabrics, under the wet load encountered in processing the yarns or fabrics, tends to remove the crimp.

Many attempts have been made to modify regenerated cellulose textiles by after-treatment of the final dried textiles with formaldehyde or a resin convertible by heat to an insoluble condition. The after-treatment of a regenerated cellulose textile which has been purified, washed and dried involves the difficulty, among others, that the modifying agent does not readily penetrate into and through the textile and it is, therefore, difiicult to obtain uniform modification of the textile throughout its crosssection. Also, in most of the after-treating methods involving the use of a resin or formaldehyde, r

any reduction in cross-sectional swelling of the regenerated cellulose fibers or yarns on immersion thereof in water is achieved at the expense of extensibility and complicates the textile processing.

It has been proposed to incorporate resin-forming ubstances in viscose or other cellulosic solutions for various purposes. For instance, it has been suggested to mix viscose with the constituents or precondensates, of urea-, phenol-, or melamineformaldehyde resins and complete the condensation by heating the article formed from the mixture. However, these constituents and the precondensates of those resins are usually soluble in the spinning baths or processing liquids used in the production of yarns by the conventional viscose process and are at least partly leached out during the spinning and afterprocessing of the yarns. For instance, the generally available melamine-formaldehyde resin precondensates are soluble in the acid spinning baths of the viscose process, from 80 to 90% of the precondensate added to the viscose initially being lost in the spinning bath and wash water. Increase in the molecular Weight of the partial condensate to a Weight at which it cannot diffuse readily from the cellulosic structure reduces the amount of the condensate lost during the spinning to about 20% but has no effect on the tenacity and swelling capacity of the textile. Moreover, modification of the cellulose requires a chemical reaction between the resin molecules with cross-bonding thereof and/or between the resin and the hydroxyl groups of the cellulose with the formation of cross-links between. the cellulose chains. In order to eifect uniform reaction between the resin molecules and/or between the resin and the hydroxyls of the cellulose, the resin should flow and align itself with the cellulose chains during extrusion of the viscose and during stretching of the yarn for orientation. Those urea-, phenol-, and melamine-formaldehyde resin precondensates which are polymerized to a stage such that they are not readily leached out of the regenerated cellulose textile are three-dimensional structures which cannot flow and align themselves with the cellulose chains but are incorporated between those chains as discrete particles. Furthermore, since the three-dimensional resin precondensates are already cross-linked structures in which most of the reactive or functional grou s are tied up and no longer available for reaction in situ in the textile, the possibility for further crossbonding of the resin molecules or cross-linking of the cellulose chains by the resin in or on the textile is greatly reduced. 1

It is an object of the present invention to provide regenerated cellulose articles of decreased water-sensitivity which pick up less water when they are immersed in water or aqueous media and therefore swell to a much less pronounced extent than conventional regenerated cellulose articles and which, on centrifuging after such immersion retain less than 50% by weight of water. Another object is to modify the water pick-up capacity, and hence the cross-sectional swelling, of regenerated cellulose textiles, and decrease the amount of water retained by the textile after centrifuging, without impairment of the capacity of the textile to regain comparative 1y small amounts of moisture from the atmosphere and without any appreciable or prohibitive loss in tensile strength or elongation. A further object is to decrease the cross-sectional swelling of regenerated cellulose textiles on immersion in water or aqueous media using a modifying polymeric material which may be added directly to viscose and which is not leached out during the spinning and processing operations. Another object is to render regenerated cellulose textiles resistant to progressive dimensional shrinkage on repeated laundering.

A still further object of the invention is: to produce regenerated cellulose articles of decreased water-sensitivity, cross-sectional swelling on immersion in water, and water-retention capacity directly from viscose having incorporated therein a resin precondensate which is in, and which remains in, reactive condition until it is converted by heat to a hardened, insoluble condition in situ on the article. Other objects will appear hereinafter.

In accordance with this invention, the water-sensitivity, cross-sectional swelling in water, and water-retention capacity of regenerated cellulose articles are decreased by bringing or converting a water-dispersible or water-soluble linear reaction product of formaldehyde and a linear polymer of a monoamide as defined hereinbelow, at least 30% by Weight of the monomeric units of which contain amide groups, to heat-hardened, insoluble condition in or on the article, The term monoamide is intended herein as a generic expression for the restricted class of related compounds which may be defined in more technical fashion as follows: a monoamide, having a single unsaturated carbon to carbon bond, of an acid of the group consisting of acrylic acid and alpha-alkyl-or beta-alkyl-substituted alpha-methylene monocarboxylic acids, and N-alkyl substituted dcrivatives thereof, the alkyl substituents consisting of methyl or ethyl,'the amide having only a single carbonyl group attached to the N atom, and at least one hydrogen atom attached to the N atom. These amides have the general formula I ll 1 12 \H wherein R, R R R are each selected from the group consisting of hydrogen, methyl, and ethyl.

The term monoamide polymer or polymer of a monoamide is intended to be generic to homopolymers and copolymers of the compounds just defined, whether they are produced directly by polymerization or copolymerization or indirectly by hydrolysis, saponification, or

other reaction upon a previously produced polymer or H copolymer.

The linear reaction product, which may also be termed a reactive condensate, a partial condensate, or a pre-con densate, may be incorporated as such in the viscose from which the article is to be formed. This is a preferred embodiment of the invention. Such partial condensates may be produced (1) by polymerizing or copolymerizing acrylamide itself or a substituted acrylamide (within the definition hereinabove) to obtain a reactive polymer of an amide and thereafter reacting the polymer with formaldehyde, or (2) by hydrolyzing a polymer or copolymer of acrylonitrile or an alkyl-substituted acrylonitrile, such as methacrylonitrile, to produce a polymeric product in which at least 30% of the monomeric units comprise amido groups. The polymeric products may be produced bystandard solution or emulsion polymerization techniques in the presence of a peroxy catalyst such as potassium persulfate.

When copolymers are used, the monomeric unit other than that containing the amide group may be considered to be derived from any other ethylenically unsaturated monomer, such as vinyl acetate, vinyl chloride, vinyl alcohol, acrylic acid, acrylonitrile, methacrylic acid, methacrylonitrile, vinylidene chloride, ethylene, etc., ormixtures thereof. Also, in using method (2), the hydrolyzedproduct may contain nitrile and/ or carboxyl groups Cit as well as amido groups if it is derived from polyacrylonitrile or from polymethacrylonitrile. It may also contain other groups, such as hydroxyl and/ or acetate groups if derived from copolymers, such as a copolymer of acrylonitrile and'vinyl acetate.

Condensation products of formaldehyde and a monoamide polymer pass through various stages from watersoluble or water-dispersible reaction products which contain reactive amido groups having at least one hydrogen on the N atom to final, heat-hardened, insoluble, condensates.

Instead of incorporating the reactive condensate in the viscose, the condensate may be formed in situ in the article by forming the article from a mixture of viscose and a reactive polymer of a monoamide and then treating the shaped article with formaldehyde. In this lastmentioned embodiment which is one of the preferred methods, the article formed from the viscose-linear poly mer' mixture is treated with aqueous formaldehyde while it is in the highly swollen gel state in which it exists after it has been subjected to the usual after-treatments including desulfiding and washing, and prior to its initial drying, so that the formaldehyde penetrates or diffuses into'the article and is available for reaction or conden sation with the polymer which occurs uniformly through-v out the article by virtue of having been extruded with the viscose.

The molecular weight of the partial condensate, or of the linear polymer of a monoamide if it is added to the viscose prior to methylolation, influences the effectiveness of the modification. When the reactive partial condensate is added to the viscose, products of relatively low molecular weight are generally most effective but they may have degrees of polymerization as high as 500 or more. For example, partial condensates which, in concentrations of 10% by weight in water containing 1% of isopropanol by weight have specific viscosities between 20 centipoises and SOOcentipoises are preferred. Partial condensates having these or lower specific viscosities are also used if the condensate is applied to a swollen gel article. On the other hand, if a monoamide polymer is mixed with the viscose for subsequent condensation with formaldehyde after shaping of the mixture, polymeric amides of relatively high molecular weight may be used and those monoamide polymers which, in concentrations of 10% in water containing 1% of isopropanol by weight have a specific viscosity of 300 centipoises to 6000 centipoises are preferred. The reactive monoamide polymers and the partial condensates of these and formaldehyde are long-chain linear substances and although they are water-dispersible at the time they are added to the viscose, and are added in the form of their water dispersions, there is no scurnming of the bath or other evidence that they are leached out during spinning or after-treating. Also, analysis for nitrogen on the final articles comprising the fully reacted condensate show that the monoamide polymers or formaldehyde-precondensates added to the viscose are retained. This is apparently attributable to the linear structure of the polymeric amides and condensates which causes them to become tangled or meshed with, and restrained from leaching out by, the cellulosic chains of the viscose. At the same time, their linear structure permits them to flow and align themselves with the cellulose chains during extrusion of the mixture and stretching of the article for orientation.

Permanent modification of the moisture pick-up and retention capacity of the regenerated cellulose yarn or the like (control of the cross-sectional swelling) is obtained by bringing the reaction between the formaldehyde and monoamide polymer to completion. This is accomplished by heating the textile or other article to curing or baking temperature. It is believed that the modification of the regenerated cellulose results primarily from reaction between the molecules of the resin-condensate aligned with the collulose chains, with the formation of bonds or bridges between the free amido groups of the condensate which bridges, or at least some of them, span the cellulose chains and serve to stabilize them, although the possibility of cross-linking of hydroxyl groups on the cellulose chains is not excluded.

The extent of reduction in water-retention, swellability and of increase in stabilization depends upon the propor tion of amido groups to total monomeric units in the molecule, the larger the proportion, the greater stabilization effect and reduction in water sensitivity. The condensates containing the lower proportions of 30 to 70% being highly useful to provide a controlled and predetermined reduction in water retention and swellability, such as is particularly desirable in the making of filter fabrics wherein a definite but limited swelling is desired to re duce the size of the interstitial spaces between the woven yarns. Condensates containing the lower proportions are also useful in the treatment of yarns produced from hollow-filament regenerated cellulose in that such treatment reduces the shrinkage of the textiles, such as fabrics, without collapsing the hollow cells. To obtain the maximum stabilization, the condensates containing higher proportions of amido groups are preferred. The condensates of polyacrylamide itself are specifically preferred because of availability, low cost, and the capacity toproduce a fully practical degree of stabilization of regenerated cellulose fabrics, yarns, fibers, etc. in a simple manner without the incorporation of an excessive amount of the condensate on the fabric.

The reaction between the formaldehyde and the monoamide polymer may be brought to completion by heating the regenerated cellulose article at a temperature of 100 to 170 C., preferably at 140 to 160 C. for a time interval between 5 and 30 minutes, and preferably in the presence of an acidic catalyst. The time of reaction should generally be inversely proportional to the temperature, 1. e., the higher the temperature, the shorter the time and vice versa. The article comprising regenerated cellulose and the reactive partial condensate of the monoamide polymer and formaldehyde may be treated with an aqueous solution of the acidic catalyst, dried, and then heated to complete the condensation, the drying and heating being performed in two stages or a single stage. Those articles formed from viscose containing a reactive monoamide polymer may be treated, in the swollen gel state,

with a neutral or alkaline solution of formaldehyde, dried, and then treated with the catalyst solution, or the article may be treated with an aqueous formaldehyde solution containing the acidic catalyst. In any case, the article to be heated to curing temperature comprises residual acidic catalyst. The amount of catalyst remaining on the article when it is cured may vary but usually when it is treated with a solution containing the catalyst in concentrations of from 0.25 to 0.50% by weight, the amount of residual acidic catalyst on the article is sufficient to catalyze the condensation of the monoamide polymer and formaldehyde. In selecting a catalyst for use in the present process, preference is given to those catalysts which catalyze the reaction of a monoamide polymer and formaldehyde, and the more highly acid catalysts which favor the reaction between formaldehyde and cellulose are preferably avoided. Any acidic catalyst which is known to catalyze ureaand melamine-formaldehyde reactions may be used. The useful catalysts may also be described as those watersoluble acids and acid salts which, in concentrations of 0.25 to 0.50% by weight in water, form aqueous solutions having a pH between 2.5 and 4, or which, on heating, dissociate to evolve a volatile base, leaving an acidic residue. Highly acid catalysts which in aqueous solution have a pH lower than 2.5 such as sulfuric acid, are preferably avoided so as to minimize direct reaction of the formaldehyde with the cellulose and also to avoid degradation of the cellulose. Examples of preferred catalysts are rnonobasic and dibasic ammonium phosphates and lactic, citric, tartaric, formic, propionic, boric and succinic acids.

The textile or the like comprising the residual acidic catalyst may be heated to curing temperature at any stage after its production. Thus, yarns may be initially dried and then heated for curing" or initially dried yarns may be woven, knitted or otherwise formed into fabrics and then heated to the curing temperature. If the yarns are in crimped condition, it is preferred to complete the condensation of the formaldehyde and the monoamide polymer after the yarns have been spun, processed and dried in relaxed condition. The heating is performed on the relaxed yarns to set the crimp and to preserve it during working up of the yarns. In other cases, it may be preferable to complete the condensation after the yarns are fabricated or during finishing of the fabrics. Fabrics comprising the regenerated cellulose yarns having the formaldehyde monoamide polymer condensate. distributed throughout their cross-section in the final heat-hardened, insoluble condition, are stabilized against progressive dimensional shrinkage on repeated laundering.

The viscose used may have any spinnable composition and may be a normal viscose having a sodium chloride said test value of from 3 to 6, containing from 6 to 9% cellulose, from 6 to 9% sodium hydroxide and of normal 6 spinning viscosity, i. e., having a ball fall viscosity of 35 seconds at 18 C.

The regenerated cellulose article may contain from 5 to 15% or more by weight (based on the weight of the cellulose in the viscose) of the formaldehyde-monoamide polymer condensate. Optimum results are obtained with about 10% of the condensate derived from polyacryl amide itself. When the polymer contains only 30 to 70% of reactive amido-containing monomeric units, a proportion of 13 to 20% is preferred if a large reduction in the water-retention and so forth is desired. The required amount of the condensate may be added directly to the viscose or the reactive polymer of a monoamide polymer may be added to it in an amount such that upon subsequent treatment of the yarn or the like formed from the viscose-polymer mixture with a solution of formaldehyde of appropriate concentration, and heating, the desired proportion of the condensate is formed in situ in the yarn.

The setting bath into which the modified viscose is extruded may be a coagulating and cellulose-regenerating bath of the composition normally used in the manufacture of fibers or yarns from viscose. Aqueous baths containing from 7 to 13.5% sulfuric acid and from 18 to 28% sodium sulfate are satisfactory. The bath may also contain comparatively small amounts, for example, from 0.1 to 5% of zinc sulfate, as well as small amounts of other adjuvants or assistants. If it is desired to produce selfcrimpable fibers of the type described in U. S. 2,517,694 to Merion and Sisson, spinning baths as described in that patent may be used. That patent points out that a spinning bath of the type just mentioned has, because of its high salt content, a rapid dehydrating action on the extruded filaments and sets up thereon an at least partially regenerated skin of substantial thickness around a still liquid or soft plastic core. This skin is set up rapidly and because of the dehydrating action of the coagulating bath has a strong tendency to shrink circumferentially so as to reduce the filament diameter. But this force is overcome by the incompressible core, whereupon the skin ruptures longitudinally along the filament, permitting part of the core to flow through the rupture. In this state the filaments are finally set up. That portion of the resulting filaments which was forced out of the core responds to subsequent stretching differently from the remainder of the filaments, as if it had originated from a different viscose. One portion of the cross-section has a thick skin showing a break along its juncture with the other portion which has a thin skin or none at all. In the crimped filaments the portion having the thick skin always takes the inside of the bends of the crimp, because of a stronger tendency to shrink. The crimped filament takes the form of a regular or irregular helical coil.

The invention is also adapted to the production of modi- :fied shaped articles by the two-bath process in which the modified viscose is extruded into a coagulating bath which effects little, if any, regeneration of the cellulose, and the article comprising cellulose xanthate is subsequently treat- I ed with a cellulose-regenerative medium.

The reactive polymer of the monoamide or formaldehyde-monoamide polymer condensate may be added to the viscose at any time but in order to avoid hydrolysis of the amide or changes in the ageing or ripening cycle for the viscose it is preferred to mix the aqueous dispersion of the modifier with the viscose after the latter has reached the predetermined spinning age, for instance by injecting the aqueous dispersion of the monoamide polymer or precondensate thereof with formaldehyde into the viscose as it is extruded through the spinneret or other forming device.

The following examples in which parts and percentages given are by weight unless otherwise stated, are illustrative of the process of the invention. These examples include tables showing the results obtained when the modified textiles were tested for water-retention, tensile trength, and elongation. In all cases, the yarns eb tained by the procedures described were weighed and conditioned at 58% relative humidity and 70 F, prior to being tested. The test for water-retention is more or less standardized and involves soaking the yarns in water, centrifuging them to remove the excess water, and weighing the yarns. The difference between the weight of the conditioned yarns prior to the soaking and centrifuging and the weight of the centrifuged yarns is a measure of the water-retention capacity of the yarns. The. specific conditions under which this test is performed may vary somewhat. In the present case, the conditioned yarns were soaked for 15 minutes in distilled water at room temperature, wrapped in a cotton muslin fabric, soaked in water for an additional 15 minutes at room tempera ture, and then centrifuged for 3 minutes in a centrifuge having a diameter of 17" and rotating at a speed of 1800 R. P. M. The results obtained by testing the waterretention capacity of the yarns by methods involving modifications of the soaking time and temperature, the centrifuging time, and the speed at which the centrifuge is rotated bear the same relationship as the values obtained under our conditions.

In the tables included in the examples, the modified yarns are compared to control yarns of regenerated cellulose which did not contain the monoamide-formaldehyde condensate but which had been conditioned for testing in the same manner as the modified yarns.

EXAMPLE I An aqueous dispersion of polyacrylamide itself which in 10% concentration in water containing 1% isopropanol on the weight of the solution, had a specific viscosity of 3200 c. p. s., was diluted to 5% polymer concentration and mixed with viscose containing 7% cellulose, 7% sodium hydroxide, and aged toa sodium chloride salt test value of 5.. The amount of the aqueous solution added to the viscose was such that the viscose contained 10% of the polyacrylamide based on the cellulose. The mixture was spun into an aqueous coagulating and regenerating bath containing 10% sulfuric acid, 4.5% zinc sulfate, and 24% sodium sulfate at about 45 C. The filaments thus formed were given a 13-inch immersion in the bath, withdrawn, and stretched 40% between godets to produce .a 150 denier, 40 filament yarn which was washed free of spinning bath. A portion of the washed yarn (A in Table I below) was soaked at room temperature in a 10% aqueous solution of formaldehyde for 5 minutes, and dried at 100 C. Another portion of the washed yarn (B in Table I) was soaked at room temperature in 10% aqueous formaldehyde containing 0.25 monobasic ammonium phosphate and dried at 100 C. The yarns comprised a reactive partial condensate of the polyacrylamide and formaldehyde. They Were heated at 150 C. for minutes to complete the condensation of the polyacrylamide and formaldehyde, scoured, and dried. They were then conditioned and tested as described above with the results shown in the table.

Table 1 Percent Tenacity,

Elongation, gJdenier percent Dry Wet Dry Wet SON.

EXAMPLE II 8 tion of the washed yarn (A in Table 11 below) was re fluxed for two hoursin-a 10% aqueous. formaldehyde solution which had been adjusted to a pH of 11 with sodium hydroxide. (B in Table II) was refluxed for two hours in a 10% aqueous solution of formaldehyde having a pH of 7. Both portions of yarn were washed in 0.5% sodium sulfite to remove free formaldehyde, rinsed, dried, and'soaked in 0.26% monobasic ammonium phosphate for 5 minutes. and, dried. The dried. yarns comprised a partial reactive condensate of the polyacrylamide and formaldehyde and residual acidic catalyst. The yarns were then heated at 150 C. for 30 minutes, scoured, dried, conditioned and tested. as in Example I. The results areshown in Table II.

Table 11 Percent Tenacity, Extensibility,

Water gjdcnier Percent Retention Dry Wet Dry Wet After the treatment with formaldehyde but prior to being treated with the acidic catalyst and heated, yarns (A) and (B) had water retentio-ns of 121.6% and 116.8% respectively.

EXAMPLE III An aqueous dispersion of a reactive partial condensate of formaldehyde and the polyacrylamide of Example. I;

which in 10% concentration in water containing 1% isopropanol' on the weight of the solution had a specific viscosity of 40 c. p. s. was mixed with viscose of normal.

viscosity containing 7% cellulose, 7% sodium hydroxide and aged to a sodium chloride salt test value of 5.

it was washed free of spinning bath it was soaked in 0.25% dibasic ammonium phosphate for 5 minutes, and dried. It was then heated at 150 C. for 30 minutes to.

These yarns (A in. Table.v

complete the condensation. III) were scoured, dried and tested for water retention with the results shown in the table.

An aqueous dispersion of the polyacrylam'ide of Example I was mixed with a viscose containing 7.4% cellulose, 7% sodium hydroxide, and aged to a sodium chloride salt test value of 5.0. The mixture was spun through a multi-hole spinneret into an aqueous bath containing 7% sulfuric acid, 1% zinc sulfate and 20% sodium. After a 13-inch immersion, the tow was with-. drawn and stretched between godets. It was washed.

sulfate.

free ofspinning bath, soaked in relaxed condition in 10% aqueous formaldehyde containing 0.25% ammonium phosphate and dried relaxed. After relaxation the filaments were in a crimped condition, and had the characteristics described in the Merion and Sisson patent, supra. The tow was heated in the relaxed condition to complete the condensation of the formaldehyde and polyacrylamide and set the filaments in the crimped state.

The crimp fixation was measured as follows: A 20 cm.

length of the yarn having a total denier of 600 (A Table IV) was suspended in a vertical position, wet-with Another portion of the washed yarn The. mixture was spun into yarn as in Example I and aftermonobasic.

water, subjected to a load of 10 gms. (16 mg./denier) and dried under the load. The load was then removed,

the yarn was again wet, and dried relaxed. The linear deformation of the yarn under the wet load minus the linear deformation of the relaxed, dried yarn was divided by the linear deformation under the wet load to obtain the percentage crimp recovery, with the results shown in table IV.

A hydrolyzed polyacrylonitrile in which about 60% of the monomeric units contained carboxyl groups, about 30% contained -CONH groups, and the balance contained nitrile groups was introduced into a viscose (at a concentration of 5% based on the weightof cellulose) of the composition as in Example I and spun into filaments as in that example. The yarn, before its first dryingwas made up into skeins and in that form was washed with Water, treated with a 1% aqueous solution of hydrochloric acid, again washed in water, soaked in a aqueous solution of formaldehyde for 5 minutes. Excess solution was removed by centrifuging; the yarn was dried at 100 C. for 30 minutes, and cured at 150 C. for 30 minutes. The product had a reduced water retention making it useful for filter fabrics. It had the following properties:

The process of Example V was repeated substituting for the hydrolyzed polyacrylonitrile, a copolymer of acrylamide and acrylic acid having in the copolymer molecule about 50% by weight of acrylamide and 50% by weight of acrylic acid. The product was similar to that of Example V.

The invention has been described in detail in connection with the production of continuous filaments, con tinuous filament yarns or fabrics comprising them. Discontinuous or staple fibers may be obtained by cutting or otherwise disrupting the modified continuous filaments or continuous filament yarns to obtain a mass of loose modified short fibers adapted to be spun into a yarn or used in the production of a non-woven fabric or feltlike article. Discontinuous or staple fibers having modified swelling properties in water may also be obtained by reducing continuous filaments or continuous filament yarns comprising the partial condensate to short fibers which may be treated with the acidic catalyst solution in bulk, after spinning into a yarn, or in fabricated structures comprising the fibers or spun yarns. Heating of the short fibers to bring the partial condensate to the finally desired insoluble state may be performed at any time after the fibers have been treated with the acidic catalyst solution.

The fibers may be heated to curing temperature in bulk if they have been treated previously with the catalyst solution, or the spun yarns or fabricated structures may be heated. Modified staple or discontinuous fibers may also be obtained by cutting or otherwise disrupting continuous filaments comprising the acrylamide polymer, thereafter treating the short fibers, in bulk, in spun yarns, in fabrics comprising the spun yarns, or in felt-like or non-woven structures with formaldehyde and the acidic catalyst, and then heating the fibers at any appropriate" stage, i. e., before or after spinning into a yarn, after fabrication of the spun yarns, or after incorporation of the fibers in non-woven or felt-like products, to complete the condensation of the acrylamide polymer and formaldehyde. Crimped staple or discontinuous fibers comprising the partial condensate and residual catalyst are set in the crimped condition provided they exist in the crimped condition when they are heated to cure the condensate. For example, when fibers comprising the partial condensate and residual catalyst and having the physical properties and cross-section of the fibers described in Merion and Sisson Patent No. 2,517,694 are heated to curing temperature in the relaxed, crimped condition, the crimp is permanently set in the fibers.

It will be apparent from the foregoing that the invention provides a new method of reliably decreasing and controlling the cross-sectional swelling of regenerated cellulose textiles When they are immersed in water or aqueous media which does not depend on after-treatments of the purified, dried textile. The process is commercially feasible because, although the monoamide polymerformaldehyde condensate remains in the reactive condition until it is cured, it is a linear product which is distributed between and meshed with the cellulose chains and therefore it is not leached from the textile by the spinning bath or processing liquids.

Various modifications and adjustments may be made in practicing the invention without departing from its spirit and scope and it is to be understood, therefore, that the invention is not to be limited except as defined by the appended claims.

I claim:

1. The method of producing a shaped article comprising regenerated cellulose and characterized by decreased water-sensitivity as compared to normal regenerated cellulose articles which comprises mixing with viscose an aqueous dispersion of a linear polymer, at least 30% of the units of which consist of an amide having the formula:

wherein R, R R R are each selected from the group consisting of hydrogen, methyl, and ethyl, coagulating and shaping the mixture and regenerating the cellulose to form an article thereof, treating the article, prior to its initial drying, with an aqueous medium comprising formaldehyde, and drying and heating the article in the presence of an acidic catalyst for the reaction of the linear polymer and formaldehyde at a temperature of C. to C. for from 5-30 minutes to produce an insoluble reaction product in situ in and distributed uniformly throughout the article.

2. Method of claim 1 wherein the aqueous medium comprising formaldehyde contains said acidic catalyst.

3. The method of producing a textile filament comprising regenerated cellulose and characterized by decreased water-sensitivity as compared to normal regenerated cellulose filaments which comprises mixing polyacrylamide with viscose immediately prior to extruding the viscose through a spinneret, extruding the mixture through a spinneret into a coagulating bath to form a filament, regenerating the cellulose in the filament, treating the filament, prior to its initial drying, with an aqueous medium comprising formaldehyde, and thereafter drying and heating the filament in the presence of an acidic catalyst for the reaction of the polyacrylamide and formaldehyde, said heating being conducted at a temperature between 100 C. and 170 C. for a time of from 5-30 minutes to produce an insoluble reaction product in situ in and distributed uniformly throughout the filament.

4. The method of claim 3, wherein the aqueous medium comprising formaldehyde also contains an acidic r1 catalyst for the reaction of the polyacrylamide and formaldehyde.

5. The process of producing a crimped fiber comprising adding to. viscose anaqueous. solution of a linear polymer, at least 30% of the units of which consist of an amide having the formula:

wherein R, R R R are each selected from the group consisting of-hydrogen, methyl, andethyl, spinning the resulting-viscose'into an aqueous coagulating bath containing-7-1=3.5% H 80 18-28% of an alkali metal sulfate, and 0.1% ZnSO recovering from the spinning bath aplurality offilament, washing these, crimping the washed filaments by soaking in relaxed condition in an aqueous formaldehyde solution containing an acidic crosslinking catalyst, and drying and heating the crimped fibers in relaxed condition to effect reaction between the linear polymer and the formaldehyde, whereby the crimp is per manently set, theresulting formaldehyde-monoamide polymer condensate being present'in an amount of 5% to 20% by weight, based on the Weight of the regenerated cellulose.

6, A-filament comprising regenerated cellulose and, distributed uniformly throughout the regenerated cellulose, 5% to 20% by Weight, based on the Weight of the regenerated cellulose, of an insoluble reaction product of formaldehyde with'a linear polymer, at least of the units of which consist of an amide having the formula:

wherein R, R R R are each selected from the group consisting of hydrogen, methyl, and ethyl, said filament being prepared by mixing with viscose an aqueous dispersion of the aforesaid linear polymer, coagulating and shaping the mixture and regenerating the cellulose to form a filament thereof, treating the filament withan aqueous medium comprising formaldehyde, and drying and heating the filament in the presence of an acidic catalyst for the reaction of the linear polymer and formaldehyde at a temperature of C. to C. for from 5 to 30 minutes to produce an insoluble reaction product in situ in and distributed uniformly throughout the filament.

7. The method which comprises, mixing viscose with.- an aqueous dispersion of a resinouslinear polymer, at? least 30% of the units of which consist of an amide having the formula wherein R is a radical selected from the group consisting of hydrogen and methyl, and R is a radical selected from the group consisting of hydrogen, methyl, and ethyl, shap ing and coagulating the mixture to forma shaped article, regenerating cellulose in the article, reacting the article with formaldehyde, and then heating the article to cure the resin.

Referencesfiited in the file of this patent UNITED STATES PATENTS 

1. THE METHOD OF PRODUCING A SHAPED ARTICLE COMPRISING REGENERATED CELLULOSE AND CHARACTERIZED BY DECREASED WATER-SENSITIVITY AS COMPARED TO NORMAL REGENERATED CELLULOSE ARTICLES WHICH COMPRISES MIXING WITH VISCOSE AN AQUEOUS DISPERSION OF A LINERA POLYMER, AT LEAST 30% OF THE UNTIS OF WHICH CONSIST OF AN AMIDE HAVING THE FORMULA: 